A memory, such as a flash memory, may have limited endurance to write/erase (W/E) cycles and may have limited data retention. As a number of W/E cycles performed in a flash memory increases, a data retention capability of the memory may be reduced and a possibility of failures may increase. For example, programming storage elements to have a high threshold voltage (e.g., corresponding to a logical “0” value) may cause faster wearing of the storage elements as compared to programming the storage elements to a lower threshold voltage or retaining the storage elements in an erased state (e.g., corresponding to a logical “1” value). To illustrate, an oxide insulation layer may wear due to electrons that pass through the oxide insulation layer during W/E cycles and generate electron trap sites. A failure may manifest as a failure to erase or program a block of the memory or may manifest as reduced data retention ability of memory cells, as illustrative examples.
In some flash memory fabrication processes, as storage element dimensions shrink, W/E cycling endurance may be reduced and may become a limiting factor that may affect commercial viability of the flash memory. For example, as memory technology is scaled down, a bit error rate (BER) of data storage of the memory generally increases. Moreover, in some cases, there may be special blocks of a flash memory, such as blocks used by flash management software or blocks used for binary caching, that experience more W/E cycles than the rest of the memory and that may be disproportionately affected by W/E cycle endurance of the memory.
Conventional approaches to control memory endurance degradation are applicable to single-level cell (SLC) type memory and rely on data (to be stored at the memory) being compressible. For example, a first conventional approach to compensate for wearing and to extend an endurance of a memory includes processing and encoding data to be stored at the memory to have more logical 1s (corresponding to a low threshold voltage) than logical 0s (corresponding to a high threshold voltage). As another example, a second conventional approach to compensate for wearing and to extend an endurance of a memory includes having stronger error correction methods and more redundant bytes. As indicated above, these conventional approaches are applicable to SLC type memory and also rely on the original data being compressible. When the conventional approaches are applied to multi-level cell (MLC) memories and all the pages of a memory word line (WL) are programmed, storage elements may be programmed to high voltage state despite the conventional approaches being applied. The programming of the storage elements to the high voltage states may cause wearing of the memory and reduce endurance of the memory.